JPH10312598A - Reproduction method and driver for magnetooptic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a reproduction method for a magnetooptic recording medium having a laminated magnetic layer in which reproduction is performed through a series of steps, i.e., transfer of a recording domain → transfer of transfer domain → reproduction of a transfer domain → reduction/extinction of transfer domain, by applying an AC field without requiring any magnetic head for generating AC field. SOLUTION: At the time of reproducing a magnetooptic recording medium having a laminate magnetic layer 3 on the surface of a basic body 2, a first pole for applying a DC field containing a component directing from the magnetic layer 3 toward the basic body 2 and a second pole for applying a DC field containing a component directing from the basic body 2 toward the magnetic layer 3 are arranged on the surface side of the magnetic layer 3 and then the magetooptic recording medium is moved relatively to the first and second electrodes. An annular magnetic head 10 can be used as the magnetic head having first and second electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium to which an alternating magnetic field must be applied for reproduction, and more particularly to a magneto-optical recording medium capable of amplifying a reproduction signal by enlarging a recording magnetic domain when reading a recording magnetic domain. The present invention relates to a method of reproducing a medium and a magneto-optical recording medium driving device using the method.

[0002]

2. Description of the Related Art In a magneto-optical recording medium, a magnetic thin film is locally heated by a laser beam or the like to reduce a coercive force.
This is a recording medium in which a magnetic domain (recording mark) is formed by reversing the magnetization direction of this portion by an external magnetic field or maintaining the initial magnetization direction, and the magnetization direction of this magnetic domain is read out by the Kerr effect and the Faraday effect. .

In a normal magneto-optical recording medium, the density of reproducible magnetic domains is limited by the spot diameter of a laser beam used for reproduction, and it is impossible to reproduce a magnetic domain having a diameter smaller than half the spot diameter. .

As a magneto-optical recording medium capable of reproducing a magnetic domain having a diameter smaller than half of the spot diameter of a laser beam, for example, JP-A-8-7350 describes a magneto-optical recording medium capable of enlarging a recording magnetic domain. . This magneto-optical recording medium has, as a recording film, a three-layer magnetic film laminated in the order of a first magnetic layer, a second magnetic layer, and a third magnetic layer from the substrate side.
The layer magnetic films are exchange-coupled. During reproduction, a laser beam is irradiated from the substrate side, while a reproducing magnetic field is applied from the recording film side. The third magnetic layer holds the recording magnetic domain, and the recording magnetic domain is transferred to the first magnetic layer and the second magnetic layer by irradiating a laser beam. The transferred magnetic domain expands in the in-plane direction of the magnetic layer by application of the reproducing magnetic field. The enlarged transfer magnetic domain is read out in the same manner as in a conventional magneto-optical recording medium. When the reproduction of the enlarged transfer magnetic domain is completed, the transfer magnetic domain is erased by applying an erasing magnetic field in a direction opposite to the reproducing magnetic field in preparation for the reproduction of the adjacent recording magnetic domain. By repeating such a process, it is possible to reproduce a minute magnetic domain, which was impossible in the past. In addition, this method not only achieves high resolution at the time of reproduction, but also actually enlarges the magnetic domain, so that the reproduction signal intensity can be essentially increased.

However, in this reproducing method, it is necessary to apply a reproducing magnetic field and an erasing magnetic field, that is, an alternating magnetic field, according to the recording density of the magnetic domain. For example, when a magnetic domain recorded by magnetic field intensity modulation is reproduced by the above method, the frequency of the alternating magnetic field at the time of reproduction is at least twice the frequency of the alternating magnetic field at the time of recording. Because there are technical and cost limitations in increasing the frequency of the magnetic field generation means,
In addition to the limit on the reproducible recording density, there is also a limit on the improvement of the transfer rate by high-speed reproduction. In addition, since it is necessary to synchronize the alternating magnetic field and the clock signal during reproduction, the medium driving device becomes complicated.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic layer having a multilayer structure and applying an alternating magnetic field.
"Transfer of the recording domain → enlargement of the transcription domain → reproduction of the transcription domain →
This is to enable reproduction without using a magnetic head that generates an alternating magnetic field when reproducing a magneto-optical recording medium that is reproduced in a series of processes of “reduction and disappearance of a transfer magnetic domain”.

[0007]

The above object is achieved by the following (1).
This is achieved by any one of the above configurations (5) to (5). (1) A method for reproducing a magneto-optical recording medium having a magnetic laminated body including at least two magnetic layers of a recording layer and an amplification layer on a surface of a substrate, wherein the surface of the substrate is irradiated with a laser beam. By applying a reproducing magnetic field substantially perpendicular to the magnetic laminate, the recording magnetic domain of the recording layer is transferred to the amplifying layer to form a transfer magnetic domain, and the transfer magnetic domain is enlarged. And then applying an erasing magnetic field substantially perpendicular to the surface of the base and opposite to the reproducing magnetic field to the transfer magnetic domain, thereby reducing and eliminating the transfer magnetic domain. A first magnetic pole for applying a DC magnetic field including a component in a direction from the magnetic laminate toward the base to continuously apply the erasing magnetic field; and a DC pole including a component in a direction from the base to the magnetic laminate. A second magnetic pole to which a magnetic field is applied is disposed on the surface side of the magnetic laminate, and a magneto-optical recording medium that moves the magneto-optical recording medium relatively to the first magnetic pole and the second magnetic pole; Playback method. (2) The reproducing method of the magneto-optical recording medium according to the above (1), wherein a pair of magnetic poles of the ring-shaped magnetic head is used as the first magnetic pole and the second magnetic pole. (3) The method for reproducing a magneto-optical recording medium according to (1) or (2), wherein the magneto-optical recording medium has a protective layer having a thickness of 0.1 μm or less on the surface side of the magnetic laminate. (4) The above (1) to (1), wherein the protective layer is a hard carbon film.
(3) The method for reproducing a magneto-optical recording medium according to any of (3). (5) A magneto-optical recording medium driving device for reproducing a magneto-optical recording medium by any one of the above-mentioned methods (1) to (4).

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reproducing Method A reproducing method of the present invention will be described with reference to FIG.

The magneto-optical recording medium 1 to be reproduced in the present invention has a magnetic laminate 3 including at least two magnetic layers on the surface side of a base 2 and a protective layer 4 on the surface side. In the illustrated example, the amplification layer A ₁ and the recording layer R ₂ are arranged from the substrate 2 side.
Are laminated to form the magnetic laminate 3. The recording layer R _2, the recording magnetic domains are formed by the optical modulation recording, or magnetic field modulation recording. To make the description easier to understand,
The recording layer R ₂ in FIG. 1, a recording magnetic domain Rd ₂ to be reproduced, are described recording magnetic domain Rd ₁ only to the adjacent preceding and reproduction is performed thereto.

A first magnetic pole for applying a DC magnetic field including a component in a direction from the magnetic laminate 3 to the substrate 2 is provided on the surface side of the substrate 2, that is, on the surface side of the magnetic laminate 3. And a second magnetic pole for applying a DC magnetic field including a component in a direction toward the stacked body. In the illustrated example, a ring-shaped magnetic head 10 is arranged as a preferred example of a magnetic head having these magnetic poles. On the other hand, an optical pickup (not shown) is disposed on the back side of the base 2, and a laser beam is irradiated through the base 2. The magneto-optical recording medium 1 moves relatively to the ring-shaped magnetic head 10 and the laser beam in the direction of the arrow in the figure. The ring-shaped magnetic head 10 is provided with a trailing-side core 12a and a leading-side core 12b via a gap 11, and a coil (not shown) is wound around at least one of the cores. Since a unidirectional current is applied to the coil, the trailing side core 12a
The magnetic field between the core 12b and the leading side core 12b is a DC magnetic field.

From the ring-shaped magnetic head 10, an arc-shaped magnetic flux as shown in FIG. Therefore, the magnetic field near the trailing core 12a and the magnetic field near the leading core 12b are in opposite directions. That is, if the magnetic field in the vicinity of the leading core 12b is in the direction from the magnetic laminate 3 to the base 2, the magnetic field in the vicinity of the trailing core 12a is in the direction from the base 2 to the magnetic laminate 3. Since the magneto-optical recording medium 1 moves relatively to the magnetic head 10 and the laser beam in the direction of the arrow in the figure, paying attention to a specific portion of the magnetic laminate 3, the magnetic field applied to the specific portion The direction will be reversed with the movement of the medium. That is, by using the ring-shaped magnetic head, it is possible to obtain the same operation and effect as when an alternating magnetic field is applied from a perpendicular magnetic head such as a magnetic head having a pot-shaped yoke.

Next, the reproducing process of the recording magnetic domain Rd ₂ will be specifically described. The magnetization direction of the recording magnetic domain Rd ₂ is upward in the figure.

First, an initialization magnetic field is applied to the magnetic laminate,
The magnetization of the entire amplification layer A ₁ previously aligned downwards. The initialization magnetic field is applied by an initialization magnetic head provided at a position apart from the illustrated ring-shaped head.

After the application of the initialization magnetic field, the recording magnetic domain Rd ₂ is irradiated with a laser beam,
An upward reproducing magnetic field in the figure is applied from 2b. The temperature of the magnetic multilayer structure is raised by laser beam irradiation, thereby recording magnetic domain Rd ₂ exchange force and is growing between the amplification layer A ₁ and the recording layer R ₂ is transferred to the amplification layer A _1, it is copied magnetic domain It is formed.
Magnetic field applied from the leading side core 12b, in order to mainly an upward component in the figure, the recording magnetic domains Rd ₂ and the copied magnetic domain is trying to expand the magnetic layer plane direction. At this time, the recording layer R ₂ has a large coercive force, the recording magnetic domain Rd ₂ is not expanded. On the other hand, the copied magnetic domains in the amplifying layer A ₁ is the interface wall exchange force, overcoming the Bloch wall exchange force and the coercive force to expand in the plane direction of the layer, the recording as shown domains Rd ₂
The transfer magnetic domain Ad has a larger diameter than the transfer magnetic domain Ad. This transfer domain A
By detecting the optical pickup reflected laser beam from d, the magnetization direction of the tiny magnetic domains Rd _2, can be detected as a large signal output.

In a series of steps of “transfer of recording magnetic domain → enlargement of transfer magnetic domain → reproduction”, the magneto-optical recording medium 1 is always moving in the direction of the arrow in the figure. After regeneration, the medium is further moved, copied magnetic domain Ad ₂ is escaped the effect of the magnetic field from the leading side core 12b, so strongly influenced by the magnetic field from the trailing-side core 12a is the magnetic field in the opposite direction . By applying a magnetic field in the opposite direction, the transfer magnetic domain Ad ₂ shrinks and disappears.

[0016] The above reproduction process, by repeating each recording magnetic domain of the recording layer R _2, in the same manner as the conventional reproduction method of applying an alternating magnetic field from the magnetic head, successively transferred and enlarged reproduction of the record magnetic domain Can be done. FIG.
In, the copied magnetic domain which has been transferred from the recording magnetic domain Rd ₁ present in the medium travel of the recording magnetic domain Rd ₂ is already extinguished by application of a magnetic field from the trailing side core 12a.

The distance between the magnetic field for transfer / amplification (reproducing magnetic field) and the magnetic field for reducing / eliminating the transfer magnetic domain (erasing magnetic field) is determined by the gap length of the ring-shaped magnetic head and the ring-shaped magnetic head. It is determined by the distance from the medium. The ring-shaped magnetic head may be in contact with the medium surface during reproduction, or may be away from the medium surface. However, in order to reproduce a minute recording magnetic domain, the distance between the ring-shaped magnetic head and the medium is preferably set to 0.1 μm or less. Therefore, when the protective layer 4 is provided as in the illustrated example, it is preferable that the thickness of the protective layer be 0.1 μm or less. When the magnetic head slides on the surface of the protective layer, a hard carbon film is preferably used as the protective layer in order to obtain a sufficient protective effect with a thickness of 0.1 μm or less.

Magneto-optical recording medium The magneto-optical recording medium to be reproduced by the present invention has a magnetic laminated body including at least two magnetic layers, and a magnetic field in a direction from the magnetic laminated body toward the base during reproduction. The other configuration is not particularly limited as long as it is necessary to alternately apply a magnetic field in the direction from the base to the magnetic laminate.
For example, the present invention can be applied to a magneto-optical recording medium having a configuration as described in JP-A-8-7350. Further, the present invention can be applied to reproduction of a magneto-optical recording medium proposed in the specification attached to the patent application (reference number 09P102) filed on Apr. 10, 1997 by the present applicant.

In the above-mentioned JP-A-8-7350,
The second magnetic layer is a rare earth transition metal alloy having a compensation temperature equal to or higher than room temperature, and the Curie temperature of the second magnetic layer is lower than the recording temperature of the minute magnetic domain. Further, the third magnetic layer is made of a rare earth transition metal alloy, and the whole magnetic moment is in the same direction at room temperature as the rare earth magnetic moment. However, according to the study of the present inventors, it has been found that it is difficult to sufficiently improve the reproduction signal intensity with the configuration of the recording film described in the publication. This is considered to be due to the fact that the exchange coupling force between the magnetic layers is too strong and the transfer magnetic domain cannot be easily expanded. In this publication, the second magnetic layer needs to be made of a rare-earth transition metal having a compensation temperature higher than room temperature. However, the compensation temperature greatly varies depending on a slight difference in composition. It is difficult to set a specific temperature range.

The present inventors have disclosed means for solving the problems in the above-mentioned Japanese Patent Application Laid-Open No. 8-73350 in the above specification attached to the patent application filed on April 10, 1997. . Among them, the means for providing the exchange force control layer or the switching layer having a specific property eliminates the need to provide a magnetic layer having a compensation temperature higher than room temperature, thereby facilitating the composition design of the magnetic layer and its formation. Further, in the above specification, even if the exchange force control layer or the switching layer is not provided and the magnetic layer having a compensation temperature higher than room temperature is not provided, the reproduced signal output is slightly lower, but the transfer / enlargement of the recording magnetic domain causes It has been disclosed that reproduction is possible. Hereinafter, the configuration of the invention disclosed in the above specification will be described in detail.

The invention disclosed in the above specification comprises the following constitutions I, II and III. Less than,
An embodiment of each configuration will be described.

The magneto-optical recording medium of the structure I structure I is the substrate surface side has a magnetic multilayer structure, the magnetic laminate, from the substrate surface side, at least amplification layer A _1, exchange force control layer C ₁₂ and recording it is intended to include magnetic layers of three layers of the layer R ₂ in this order. The recording layer R ₂ are magnetic domains are formed by magneto-optical recording. When reproducing the magneto-optical recording medium, first, an initialization magnetic field in a direction perpendicular to the magnetic laminated body is applied. Then, by irradiating a laser beam, sequentially transferred to form a transfer magnetic domains and a magnetic domain of the recording layer R ₂ from the exchange force control layer C ₁₂ to the amplification layer A _1, at the same time, amplifying layer by applying a reproducing magnetic field expanding the copied magnetic domain of a _1. The direction of the reproducing magnetic field is opposite to the direction of the initialization magnetic field. Then, read the expanded transferred magnetic domain in the amplification layer A _1. Then, the copied magnetic domains play is complete, the direction of magnetization by applying an inverse of the erasing magnetic field and the reproducing magnetic field, reducing the transfer magnetic domains of the amplification layer A _1, extinguish. Subsequently, the magnetic domain adjacent to the magnetic domain whose reproduction has been completed is reproduced.

Reproducing Process (Configuration I) When the magnetization of the magnetic domain is in the same direction as the reproducing magnetic field FIG. 2 is a schematic diagram showing the direction of the magnetization of each magnetic layer in the magnetic laminate. In the figure, the white arrow indicates the direction of magnetization of the entire magnetic layer, and the black arrow indicates the spin direction of the transition metal element in the magnetic layer. This is the same in other schematic diagrams of the magnetic laminate. Amplification layer A ₁ in the present invention, either no compensation temperature, compensation temperature so below room temperature, so that the direction of the double arrow match. Note that the recording layer R ₂ may have a compensation temperature higher than room temperature.

Firstly, among the recorded on the recording layer R ₂ domains, domains with the same direction of the magnetization and the reproducing magnetic field, that is, the reproduction of the magnetic domain having an upward magnetization in the figure 2 will be described.

FIG. 2 (a): As shown in the state after the recording Figure 2 (a), the magnetic domain is formed by a magneto-optical recording in the recording layer R _2. The amplification layer A ₁ is the interface wall exchange force, magnetic domains having a spin in the same direction as the recording layer R ₂ is formed. Incidentally, the exchange force control layer C ₁₂ is to act as a domain wall, its composition, thickness, etc. are set.

FIG. 2 (b): to initialize the magneto-optical recording medium in this state, as shown in FIG. 2 (b), applying an initializing magnetic field H _I. The initialization magnetic field is applied by an initialization magnetic head. The initialization magnetic head is arranged at a position apart from a reproduction magnetic head described later. By the application of the initialization magnetic field H _I , the directions of the magnetizations of the amplification layer A ₁ and the exchange force control layer become the same as those of the initialization magnetic field.

FIG. 2 (c): after transferring initializing magnetic field applying magnetic domain, while applying a reproducing magnetic field H _R, irradiating a laser beam to the medium. A reproducing magnetic head for applying a reproducing magnetic field and an optical pickup for irradiating a laser beam are usually arranged to face each other with a medium therebetween. The laser beam is emitted from the substrate side. Reproduction magnetic field H
_R is opposite to the initialization magnetic field H _I.

The temperature of each magnetic layer rises by the laser beam irradiation, and the interface domain wall exchange force between adjacent magnetic layers increases. Thus, the recording magnetic domain of the recording layer R ₂ is transferred to the amplification layer A _1, copied magnetic domain is formed. The orientation of magnetization of the formed amplified layer A ₁ copied magnetic domain is opposite to the initializing magnetic field orientation.

FIG. 2 (d): The expansion each magnetic layer of the transfer magnetic domain since the reproducing magnetic field H _R in the same direction as the magnetization of the magnetic domain is applied, magnetic domains of the magnetic layers is trying to expand in the plane direction of the layer Although the, at this time, without a larger magnetic domain in the recording layer R _2, to enlarge the magnetic domain in the amplification layer a _1. For this, for example, the recording layer R _2, does not expand the magnetic domain by setting to indicate the high coercive force even at temperatures at the time of laser beam irradiation. Further, for example, the amplification layer A _1,
Enough to expand the magnetic domain overcomes the the Bloch wall exchange force field and the coercive force is set so that the interface wall exchange force is weakened between the recording layer R _2.

[0030] After the enlarged copied magnetic domain of the amplification layer A _1, read by the magnetic Kerr effect this.

FIGS. 2 (e) and 2 (f): Reduction and elimination of transfer magnetic domain
After utilizing the dark magnetic Kerr effect read the copied magnetic domain of the amplification layer A _1, erasing magnetic field H magnetization orientation is opposite to the reproducing magnetic field
_{Apply E.} By orientation of magnetization of the copied magnetic domain is to apply a reverse of erasing magnetic field H _E, copied magnetic domain is reduced as shown in FIG. 2 (e), further, it disappears as shown in FIG. 2 (f), The magnetization of the area that was the transfer domain has the same direction as the surroundings,
That return to the direction of the initialization magnetic field H _I. As a result, FIG.
It returns to the state of (b).

[0032] When the magnetization of the magnetic domain is reproduced magnetic field opposite Next, among the recorded on the recording layer R ₂ domains, domains with the magnetization of the reproducing magnetic field and the reverse, i.e., indicated by the downward arrow in the figure 2 The reproduction of the magnetic domain having the magnetization to be performed will be described.

Also in this case, the magnetic domain of the recording layer R ₂ is the same as that of the amplification layer A _1.
Are transcribed, the copied magnetic domains formed so have a magnetization in the same direction as the initializing magnetic field, the magnetization state of the amplification layer A ₁ is not changed, it maintains the same magnetization state through the regeneration process. In this state, read by the magnetic Kerr effect the magnetization direction of the amplification layer A _1. In the reproduction process of the magnetic domain, it is necessary that the magnetization of the transfer domain is not reversed during the entire process.

Reproduction Conditions (Configuration I) In order to perform reproduction in the above-described process, the temperature of the magnetic laminate at the time of irradiating a laser beam during reproduction must be
It is necessary that the magnetic domain in the amplification layer A ₁ recording layer R ₂ is unaffected is transferred. For this purpose, the Curie temperature Tc _A1 Curie temperature Tc _A1 of the amplification layer A ₁ is preferably lower than the Curie temperature Tc _R2 of the recording layer R _2. Also,
Tc _A1 needs to be higher than room temperature. This is the same in the configuration II and the configuration III described later.

In the configuration I, if the Curie temperature of the amplification layer A ₁ is Tc _A1 and the Curie temperature of the exchange force control layer C ₁₂ is Tc _C12 , Tc _A1 <Tc _C12 . By providing an exchange force control layer C ₁₂ having such characteristics, enlargement of the copied magnetic domain in the amplification layer A ₁ is extremely easy.

[0036] The coercive force in the transfer condition I amplification layer A ₁ Hc _A1, the demagnetizing field and Hd _A1, the interface wall exchange force field between the recording layer R ₂ of the amplification layer A ₁ and Hw _A1R2, during transfer when the reproducing magnetic field intensity was Hr, in order to transfer the magnetic domain from the recording layer R ₂ to the amplification layer a ₁ is sufficiently performed, the formula _{(I-1) Hw A1R2 +} Hr> Hc A1 -Hd A1 is satisfied Need to be

Since the temporal change of the reproducing magnetic field intensity usually becomes a sine curve, Hr under each condition described in this specification is not always the same value.

The interface magnetic wall exchange force magnetic field is Hw _A1R2 = _{σw A1R2} / 2Ms _A1 t _A1 when Hw _A1R2 is _taken as an example. .sigma.w _A1R2 are interface wall energy between the recording layer R ₂ adjacent thereto and the amplification layer A _1, it is synonymous even if you have labeled σw _R2A1. Ms _A1 is the saturation magnetization of the amplification layer A ₁ , and ts _A1 is the thickness of the amplification layer A ₁ . The exchange force control layer C ₁₂ functions as a domain wall and has a role of controlling _{σw A1R2} .

The condition represented by the above formula (I-1) needs to be similarly satisfied whether the magnetization direction of the magnetic domain is the same as or opposite to the reproducing magnetic field.

[0040] When the magnetization of the copied magnetic domain of the non-inverting condition I amplification layer A ₁ is reproducing magnetic field and the reverse, even by applying a reproducing magnetic field need not reversed magnetization of the copied magnetic domain. The condition for this (non-reversal condition) is expressed by the following equation (I-2), where Hr is the intensity of the reproducing magnetic field, and Hr <Hw _A1R2 + Hc _A1 −Hd _A1 .

[0041] When the magnetization of the copied magnetic domain expansion conditions I amplification layer A ₁ are in the same direction as the reproducing magnetic field, by applying the reproducing magnetic field, it is necessary to expand the copied magnetic domain. Conditions for expanding the copied magnetic domain of the amplification layer A ₁ (enlargement condition) of the formula (I-3) a Bloch wall exchange force field of the amplification layer A ₁ as Hw _A1 Hr> Hw _A1R2 -Hd _A1
+ Hw _A1

The copied magnetic domain extinction condition I amplification layer A ₁ must not disappear when the magnetic domain adjacent to the plane direction reproduction. When the magnetization of the copied magnetic domain is the same direction as the reproducing magnetic field, condition for extinction is transferred magnetic domains in the presence of erasure magnetic field H _E (extinction condition),
_Assuming that the intensity of the erasing magnetic field is He, the equation (I-4) is expressed by He> Hw _A1R2 −Hd _A1 + Hw _A1 .

[0043] for transferring the magnetic domain of the non-transfer conditions I amplification layer A ₁ is not transferred to the amplification layer A ₁ again domain of the recording layer R ₂ is when extinguished condition (non-transfer condition), the formula (I-5) Hw _A1R2 <Hc _A1 −Hd _A1 + He.

[0044] In condition amplification layer A ₁ of the amplification layer A _1, in order to satisfy the the above expanded condition and a non-inverting condition at the same temperature, the formula (I-2) Hr <Hw A1R2 + Hc A1 -Hd A1 , formula (I-3) Hr> Hw A1R2 -Hd A1 + Hw A1 and simultaneously satisfying that a, that is, satisfying the formula _{(I-6) Hc A1>} Hw A1 at the temperature at which the copied magnetic domain of the amplification layer a ₁ is expanded It is necessary to.

The magneto-optical recording medium of the structure II configuration II, in addition to providing the switching layer S ₁₂ in place of the exchange force control layer C ₁₂ is the same as the configuration I. Switching layer S _12, the Curie temperature Tc _S12
There is a lower magnetic layer than the Curie temperature Tc _A1 of the amplification layer A ₁ higher than room temperature.

The details of the reproducing process and the conditions necessary for the reproducing in the structure II will be described below.

[0047] When the magnetization of the reproduction process (configuration II) magnetic domains in the same direction as the reproducing magnetic field is first, among the recorded on the recording layer R ₂ domains, domains with the magnetization in the same direction as the reproducing magnetic field, i.e. in the figure 3 Reproduction of a magnetic domain having a magnetization indicated by an upward white arrow will be described.

[0048] FIG. 3 (a): the state switching layer S ₁₂ after recording, the recording layer R by the interface wall exchange force
₂ (a) except that a magnetic domain having the same magnetization direction as that of ₂ is formed.

[0049] FIG. 3 (b): The application of the initialization initializing magnetic field H _I, except that the same as the direction of even initializing magnetic field the direction of magnetization of the switching layer S ₁₂ is 2
Same as (b).

FIG . 3 (c): Transfer of magnetic domain As in FIG. 2 (c), after applying the initializing magnetic field, the reproducing magnetic field H _R
While applying the laser beam, the medium is irradiated with a laser beam.

The temperature of each magnetic layer rises due to the laser beam irradiation, and the interface domain wall exchange force between the recording layer R ₂ and the switching layer S ₁₂ and the interface domain wall exchange between the switching layer S ₁₂ and the amplification layer A ₁ are increased. Strengthens. Thereby, the recording layer R
_Second recording magnetic domain, the switching layer S _12, are sequentially transferred to the amplification layer A _1, the layers copied magnetic domains are formed. The magnetization of the transfer domain of each layer is opposite to the initialization magnetic field.

FIG . 3D : Enlarged magnetic domain in the enlarged recording layer R ₂ of the transferred magnetic domain , and the amplification layer A ₁
In the case of expanding the magnetic domain in FIG.
Is the same as

[0053] Curie temperature of the switching layer S _12, it is preferable than the temperature at the time of the magnetic domain transfer is high, and the amplification layer A ₁ is less than the temperature at which the force of magnetic domain expansion work. Domain transfer occurs in the Atsushi Nobori process by laser beam irradiation, but after the magnetic domain transferred even up the temperature of the magnetic layer is copied magnetic domain of the amplification layer A ₁ is to expand, the magnetization of the switching layer S ₁₂ is lost in this case if you set the Curie temperature as is, amplified layer a ₁ is not affected by exchange force between the recording layer R _2, it is easy to expand the copied magnetic domain.

[0054] After the enlarged copied magnetic domain of the amplification layer A _1, read by the magnetic Kerr effect this.

FIGS. 3 (e) and 3 (f): Reduction and elimination of transfer magnetic domains.
After reading the copied magnetic domain of the amplification layer A ₁ using the dark magnetic Kerr effect, applies an erase magnetic field H _E similarly to the structure I. As a result, the transfer magnetic domain of the amplification layer A ₁ is reduced and disappears due to the Bloch domain wall exchange force, and the magnetization of the region that was the transfer magnetic domain is
Same direction as the surrounding, i.e. back in the direction of the initializing magnetic field H _I. On the other hand, the switching layer S _12, the temperature is lowered by the movement of the laser beam, the magnetization occurs, the magnetization of this time, and erasing magnetic field H _E, by the exchange force between the amplification layer A _1, amplification layer A _The direction is the same as ₁ , that is, the direction of the initialization magnetic field. As a result, the magnetization state of each magnetic layer changes as shown in FIG.
State will be restored.

[0056] When the magnetization of the magnetic domain is reproduced magnetic field opposite Next, among the recorded on the recording layer R ₂ domains, domains with the magnetization of the reproducing magnetic field and the reverse, i.e., indicated by the downward arrow in the figure 3 The reproduction of the magnetic domain having the magnetization to be performed will be described.

Also in this case, the magnetic domain of the recording layer R ₂ is transferred to the switching layer S ₁₂ and the amplification layer A _1. However, since the transferred magnetic domain has the same magnetization as the initialization magnetic field, the amplification layer A
The magnetization state of ₁ does not change, and maintains the same magnetization state throughout the reproducing process. In this state, read by the magnetic Kerr effect the magnetization direction of the amplification layer A _1. This magnetic domain of the reproduction process, it is necessary that the magnetization of the copied magnetic domain in the amplification layer A ₁ is not reversed throughout the process.

[0058] The coercive force in the reproduction condition (configuration II) transfer conditions II amplification layer A ₁ and Hc _A1, the demagnetizing field Hd _A1, the coercive force Hc _S12, the demagnetizing field and Hd _S12 in the switching layer S _{1 2,} switching Hw _S12R2 the interface wall exchange force field between the recording layer R ₂ layers S _12, Hw an interface wall exchange force field between the switching layer S _{1 2} amplification layer a _1
A1S12, and when the reproducing magnetic field strength during transfer is Hr,
To transfer the magnetic domain from the recording layer R ₂ to the switching layer S ₁₂ is sufficiently performed, the formula _{(II-1-1) Hw S12R2 +} Hr> Hc S12 -Hd
_S12 must is satisfied, because the magnetic domain transferred from the switching layer S ₁₂ to the amplification layer A ₁ is sufficiently performed, the formula _{(II-1-2) Hw A1S12 +} Hr> Hc A1 -Hd A1 is Need to be satisfied.

The formulas (II-1-1) and (II-1)
The condition represented by -2) must be satisfied in the same manner regardless of whether the magnetization direction of the magnetic domain is the same as or opposite to the reproducing magnetic field.

Non-Reversal Condition II When the magnetization of the transfer magnetic domain is in the opposite direction to the reproducing magnetic field, it is necessary that the magnetization of the transfer magnetic domain does not reverse even when the reproducing magnetic field is applied. Conditions for this (non-inverted condition), when the intensity of the reproducing magnetic field and the Hr, formula (II-2-1) for switching layer _{S 12 Hr <Hw S12R2 + Hc} S12 -Hd
Expressed in _S12, the amplification layer A ₁ is represented by formula (II-2-2) Hr <Hw A1S12 + Hc A1 -Hd A1. However, when enlarging the copied magnetic domain, because the magnetic layer temperature is equal to or greater than the Curie temperature of the switching layer S _12, the formula (II-2-1) has no meaning, also, is Hw _A1S12 Since it becomes zero, the above equation (II-2-
2) becomes the formula (II-2-2 ') Hr <Hc _A1 -Hd _A1 .

[0061] When the magnetization of the enlargement condition II transcription domains are in the same direction as the reproducing magnetic field, by applying the reproducing magnetic field, it is necessary to expand the copied magnetic domain of the amplification layer A _1. Conditions for this (enlargement condition), considering that the switching layer S ₁₂ is in the Curie temperature or higher, the Bloch wall exchange force field of the amplification layer A ₁ H
W _a1 is represented by the formula (II-3) Hr> Hw _A1 −Hd _A1 .

[0062] copied magnetic domain extinction condition II amplification layer A ₁ must not disappear when the magnetic domain adjacent to the plane direction reproduction. When the magnetization of the copied magnetic domain is the same direction as the reproducing magnetic field, the conditions for transferring the magnetic domain of the amplification layer A ₁ in the presence of erasing magnetic field H _E disappears (extinction condition), the intensity of the erasing magnetic field was He At this time, the expression (II-4) is expressed by He> Hw _A1S12 -Hw _A1 -Hd _A1 .

[0063] When the temperature of the non-transfer conditions II switching layer S ₁₂ drops to below the Curie temperature, the condition for magnetic domain of the recording layer R ₂ to the switching layer S ₁₂ is not transferred again (non-transfer condition), the formula ( II-5) Hw _S12R2 <Hc _S12 −Hd _S12 + He.

Conditions for the Amplification Layer A _{1 In} order to satisfy the above-mentioned enlargement condition and the non-inversion condition at the same temperature, the following expression (II-2-2 ′) Hr <Hc _A1 −Hd _A1 and the expression (II-3) ) Hr> Hw _A1 -Hd _A1 and simultaneously satisfying that, i.e., it is necessary at the temperature at which the copied magnetic domain of the amplification layer a ₁ is enlarged to satisfy the formula _{(II-6) Hc A1>} Hw A1.

[0065] The magneto-optical recording medium of the structure III configuration III, except that without the exchange force control layer C ₁₂ is the same as the configuration I. That is, the amplification layer A ₁
Is a composition that does not have a compensation temperature higher than room temperature.

[0066] without providing an exchange force control layer C _12, in the process from the transfer of the magnetic domain to its expansion, after the exchange force between the recording layer R ₂ amplification layer A ₁ becomes temporarily high, decreasing as long as it is possible to easily enlarge the copied magnetic domain of the amplification layer a _1.

Configuration of Each Magnetic Layer Details of the configuration of each magnetic layer will be described. Various configurations such as the composition and thickness of each magnetic layer may be appropriately determined so as to satisfy the above-described conditions, and are not limited.
Preferably, it is set as follows.

Amplification Layer A ₁ A main component is a rare earth metal element and a transition metal element. The rare earth metal element preferably contains at least Gd and / or Dy, and the transition metal element preferably contains at least Fe and / or Co. The thickness is preferably from 10 to 100 nm. If the thickness is too thin, information of other magnetic layers is read through the amplification layer at the time of reproduction, resulting in a low C / N.
On the other hand, if it is too thick, the interface domain wall exchange force magnetic field for the amplification layer cannot be increased, and the transfer of the magnetic domain becomes insufficient. The Curie temperature is preferably from 80 to 300 ° C.

The recording layer R ₂ contains a rare earth metal element and a transition metal element as main components. The rare earth metal element preferably contains at least Tb, and the transition metal element preferably contains at least Fe and Co. The thickness is preferably at least 10 nm. If it is too thin, the recording magnetic domain becomes unstable, so that recording becomes substantially impossible. Although there is no particular upper limit for the thickness, it is not necessary to set the thickness to more than 100 nm to increase costs. Curie temperature is 80 ~ 400 ℃
It is preferred that

Exchange Force Control Layer C ₁₂ Mainly contains a rare earth metal element and a transition metal element. The rare earth metal element preferably contains at least Gd and / or Dy, and the transition metal element preferably contains at least Fe and / or Co. The thickness is preferably from 5 to 50 nm. If it is too thin, the above-described exchange force control effect will be insufficient. On the other hand, if too thick, so can not be domain wall the whole exchange force control layer C _12, it will not achieve the exchange force control effects described above. The Curie temperature is preferably 80 ° C. or higher.

Switching layer S ₁₂ Mainly contains a rare earth metal element and a transition metal element. The rare earth metal element preferably contains at least Gd and / or Dy, and the transition metal element preferably contains at least Fe and / or Co. The thickness is preferably from 5 to 50 nm. If it is too thin, it will be difficult to block the exchange force. on the other hand,
If the thickness is too large, the interface domain wall exchange force magnetic field becomes small, so that the transfer of magnetic domains becomes insufficient. Curie temperature is 80 ~ 300
C. is preferred.

[0072] enhancement layer E ₀₁ enhancement layer is the side closest to the base of the magnetic multilayer structure, i.e., between the amplification layer A ₁ and the substrate, a magnetic layer which is provided if necessary. The enhancement layer has the effect of enhancing the Kerr effect. Curie temperature of enhanced layer E ₀₁ is Tc
_E01, when the Curie temperature of the amplification layer A ₁ and the Tc _A1, needs to be Tc _A1 <Tc _E01. If this relationship is not satisfied, the Kerr effect cannot be enhanced. Curie temperature is 300
It is preferable that the temperature is not lower than ° C.

The enhance layer contains a rare earth metal element and a transition metal element as main components. As rare earth metal elements,
It is preferable that at least Gd be contained, and that the transition metal element be at least Fe and Co. The thickness is preferably from 5 to 50 nm.
If it is too thin, the enhancement effect will be small. On the other hand, if it is too thick, it will affect the characteristics of the amplification layer, making it difficult to reproduce along the process described above.

Dielectric Layer In the magneto-optical recording medium having the above structure, a dielectric layer is usually provided between the substrate and the magnetic laminate, that is, on the back side of the magnetic laminate. Although a dielectric layer may be provided on the front side of the magnetic laminate as necessary, the distance between the magnetic head and the magnetic laminate becomes large. No layers are provided. The dielectric layer has a function of protecting the magnetic laminate and a function of enhancing the Kerr effect and the Faraday effect. The dielectric layer may be made of various metal oxides, metal nitrides, metal sulfides, mixtures of these metal compounds, and the like, similarly to a normal magneto-optical recording medium. The thickness of the dielectric layer provided on the back side of the magnetic laminate is usually 30
The thickness of the dielectric layer provided on the surface side of the magnetic laminate is generally about 10 to 100 nm.

Reflective Layer On the surface side of the second dielectric layer, a reflective layer is provided if necessary. The reflection layer also functions as a heat dissipation layer. The thickness of the reflection layer is usually set to about 10 to 200 nm.

Substrate In the magneto-optical recording medium to which the present invention is applied, since the reproducing light enters from the back side of the substrate, the substrate needs to be substantially transparent to the reproducing light. For this reason, it is preferable that the base is made of resin, glass, or the like.

[0077]

As EXAMPLE substrate, using the outside diameter 120 mm, a thickness of 1.2mm disc-shaped polycarbonate (track pitch 1.1 .mu.m), to produce a magneto-optical recording disk sample by the following procedure.

Dielectric Layer In a Ar + N ₂ atmosphere, a silicon nitride film was formed by sputtering using Si as a target to form a dielectric layer. The thickness was 60 nm.

The amplification layer was formed by a sputtering method using a Gd—Fe—Co alloy target in an A ₁ Ar atmosphere. The thickness was 40 nm.

The recording layer was formed in a R ₂ Ar atmosphere by a sputtering method using a Tb—Fe—Co alloy target. The thickness was 40 nm.

The protective layer was formed by sputtering using C as a target in an atmosphere of Ar + H ₂ . The thickness was 50 nm.

Characteristic evaluation The characteristics of this sample were evaluated using an optical disk evaluation device. The measurement conditions were as follows.

Recording conditions Laser wavelength: 680 nm, aperture ratio NA: 0.55, recording power: 8 mW, recording magnetic field: 300 Oe, relative linear velocity: 8 m / s, light modulation recording: frequency 8 MHz

Reproduction conditions Laser wavelength: 680 nm, aperture ratio NA: 0.55, reproduction power: 2.5 mW, initialization magnetic field: 2000 Oe, ring head (gap length 0.
2 μm) and a relative linear velocity of 3.2 m / s, a magnetic field (500O) corresponding to an alternating magnetic field of a frequency of 16 MHz.
e) was applied.

At the time of reproduction, the ring head was made to slide on the surface of the protective layer of the sample. As a result, 4
A C / N of 5 dB was obtained.

COMPARATIVE EXAMPLE The sample prepared in the above example was reproduced in the same manner as in the above example except that the reproducing power was 1.5 mW and no reproducing / erasing magnetic field was applied. Was 40 dB. From this result, it can be seen that the application of the magnetic field from the ring head in the above example exhibited the same effect as the application of the alternating magnetic field.

[0087]

According to the present invention, when reproducing a magneto-optical recording medium capable of improving the high-density recording and the data transfer rate and essentially increasing the reproduction signal output,
By using the DC magnetic field from the ring-shaped magnetic head without using the magnetic head that generates the alternating magnetic field, the same operation and effect as the application of the alternating magnetic field can be obtained. Therefore, according to the present invention, a high-frequency magnetic field generator is not required for the driving device, and the driving device can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a reproduction method of the present invention.

FIGS. 2A to 2F are diagrams schematically illustrating a reproducing process of a magneto-optical recording medium to which a reproducing method of the present invention is applied.

FIGS. 3A to 3F are diagrams schematically illustrating a reproducing process of a magneto-optical recording medium to which the reproducing method of the present invention is applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Magneto-optical recording medium 2 Substrate 3 Magnetic laminated body 4 Protective layer 10 Ring-shaped magnetic head 11 Gap 12a Trailing side core 12b Leading side core A ₁ Amplification layer R ₂ Recording layers Rd ₁ , Rd ₂ Recording magnetic domain Ad Transfer magnetic domain

Claims (5)

[Claims] 1. A method for reproducing a magneto-optical recording medium having a magnetic laminated body including at least two magnetic layers, a recording layer and an amplification layer, on a surface of a substrate, comprising: By applying a reproducing magnetic field substantially perpendicular to the substrate surface to the magnetic laminate, a recording magnetic domain of the recording layer is transferred to the amplification layer to form a transfer magnetic domain, and the transfer magnetic domain is enlarged. Reading the transfer magnetic domain, and then applying an erasing magnetic field substantially perpendicular to the substrate surface and opposite to the reproducing magnetic field to the transfer magnetic domain,
A first step of applying a DC magnetic field including a component in a direction from the magnetic laminate to the base in order to continuously apply the reproducing magnetic field and the erasing magnetic field. And a second magnetic pole for applying a DC magnetic field including a component in a direction from the base toward the magnetic laminate, are disposed on the surface side of the magnetic laminate, and the first magnetic pole and the second magnetic pole are arranged. A method for reproducing a magneto-optical recording medium, in which the magneto-optical recording medium is relatively moved. 2. The method according to claim 1, wherein a pair of magnetic poles of the ring-shaped magnetic head is used as the first magnetic pole and the second magnetic pole. 3. The reproducing method for a magneto-optical recording medium according to claim 1, wherein the magneto-optical recording medium has a protective layer having a thickness of 0.1 μm or less on a surface side of the magnetic laminated body. 4. The method according to claim 1, wherein the protective layer is a hard carbon film.
3. A reproducing method for a magneto-optical recording medium according to any one of the above-mentioned items. 5. A magneto-optical recording medium driving device for reproducing a magneto-optical recording medium by the method according to claim 1.